package com.java8.stream;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.IntSummaryStatistics;
import java.util.List;
import java.util.Random;
import java.util.stream.Collectors;

public class Main {

	public static void main(String args[]){
	      System.out.println("使用 Java 7: ");
	        
	      // 计算空字符串
	      List<String> strings = Arrays.asList("abc", "", "bc", "efg", "abcd","", "jkl");
	      System.out.println("列表: " +strings);
	      long count = getCountEmptyStringUsingJava7(strings);
	        
	      System.out.println("空字符数量为: " + count);
	      count = getCountLength3UsingJava7(strings);
	        
	      System.out.println("字符串长度为 3 的数量为: " + count);
	        
	      // 删除空字符串
	      List<String> filtered = deleteEmptyStringsUsingJava7(strings);
	      System.out.println("筛选后的列表: " + filtered);
	        
	      // 删除空字符串，并使用逗号把它们合并起来
	      String mergedString = getMergedStringUsingJava7(strings,", ");
	      System.out.println("合并字符串: " + mergedString);
	      List<Integer> numbers = Arrays.asList(3, 2, 2, 3, 7, 3, 5);
	        
	      // 获取列表元素平方数
	      List<Integer> squaresList = getSquares(numbers);
	      System.out.println("平方数列表: " + squaresList);
	      List<Integer> integers = Arrays.asList(1,2,13,4,15,6,17,8,19);
	        
	      System.out.println("列表: " +integers);
	      System.out.println("列表中最大的数 : " + getMax(integers));
	      System.out.println("列表中最小的数 : " + getMin(integers));
	      System.out.println("所有数之和 : " + getSum(integers));
	      System.out.println("平均数 : " + getAverage(integers));
	      System.out.println("随机数: ");
	        
	      // 输出10个随机数
	      Random random = new Random();
	        
	      for(int i=0; i < 10; i++){
	         System.out.println(random.nextInt());
	      }
	        
	      System.out.println("使用 Java 8: ");
	      System.out.println("列表: " +strings);
	        
	      count = strings.stream().filter(string->string.isEmpty()).count();
	      System.out.println("空字符串数量为: " + count);
	        
	      count = strings.stream().filter(string -> string.length() == 3).count();
	      System.out.println("字符串长度为 3 的数量为: " + count);
	        
	      filtered = strings.stream().filter(string ->!string.isEmpty()).collect(Collectors.toList());
	      System.out.println("筛选后的列表: " + filtered);
	        
	      mergedString = strings.stream().filter(string ->!string.isEmpty()).collect(Collectors.joining(", "));
	      System.out.println("合并字符串: " + mergedString);
	        
	      squaresList = numbers.stream().map( i ->i*i).distinct().collect(Collectors.toList());
	      System.out.println("Squares List: " + squaresList);
	      System.out.println("列表: " +integers);
	        
	      IntSummaryStatistics stats = integers.stream().mapToInt((x) ->x).summaryStatistics();
	        
	      System.out.println("列表中最大的数 : " + stats.getMax());
	      System.out.println("列表中最小的数 : " + stats.getMin());
	      System.out.println("所有数之和 : " + stats.getSum());
	      System.out.println("平均数 : " + stats.getAverage());
	      System.out.println("随机数: ");
	        
	      random.ints().limit(10).sorted().forEach(System.out::println);
	        
	      // 并行处理
	      count = strings.parallelStream().filter(string -> string.isEmpty()).count();
	      System.out.println("空字符串的数量为: " + count);
	   }
	    
	   private static int getCountEmptyStringUsingJava7(List<String> strings){
	      int count = 0;
	        
	      for(String string: strings){
	        
	         if(string.isEmpty()){
	            count++;
	         }
	      }
	      return count;
	   }
	    
	   private static int getCountLength3UsingJava7(List<String> strings){
	      int count = 0;
	        
	      for(String string: strings){
	        
	         if(string.length() == 3){
	            count++;
	         }
	      }
	      return count;
	   }
	    
	   private static List<String> deleteEmptyStringsUsingJava7(List<String> strings){
	      List<String> filteredList = new ArrayList<String>();
	        
	      for(String string: strings){
	        
	         if(!string.isEmpty()){
	             filteredList.add(string);
	         }
	      }
	      return filteredList;
	   }
	    
	   private static String getMergedStringUsingJava7(List<String> strings, String separator){
	      StringBuilder stringBuilder = new StringBuilder();
	        
	      for(String string: strings){
	        
	         if(!string.isEmpty()){
	            stringBuilder.append(string);
	            stringBuilder.append(separator);
	         }
	      }
	      String mergedString = stringBuilder.toString();
	      return mergedString.substring(0, mergedString.length()-2);
	   }
	    
	   private static List<Integer> getSquares(List<Integer> numbers){
	      List<Integer> squaresList = new ArrayList<Integer>();
	        
	      for(Integer number: numbers){
	         Integer square = new Integer(number.intValue() * number.intValue());
	            
	         if(!squaresList.contains(square)){
	            squaresList.add(square);
	         }
	      }
	      return squaresList;
	   }
	    
	   private static int getMax(List<Integer> numbers){
	      int max = numbers.get(0);
	        
	      for(int i=1;i < numbers.size();i++){
	        
	         Integer number = numbers.get(i);
	            
	         if(number.intValue() > max){
	            max = number.intValue();
	         }
	      }
	      return max;
	   }
	    
	   private static int getMin(List<Integer> numbers){
	      int min = numbers.get(0);
	        
	      for(int i=1;i < numbers.size();i++){
	         Integer number = numbers.get(i);
	        
	         if(number.intValue() < min){
	            min = number.intValue();
	         }
	      }
	      return min;
	   }
	    
	   private static int getSum(List numbers){
	      int sum = (int)(numbers.get(0));
	        
	      for(int i=1;i < numbers.size();i++){
	         sum += (int)numbers.get(i);
	      }
	      return sum;
	   }
	    
	   private static int getAverage(List<Integer> numbers){
	      return getSum(numbers) / numbers.size();
	   }
}
